J. Nikbakht; V. Eshghi; T. Barzegar; A.R. Vaezi
Abstract
Introduction: In arid and semi-arid regions such as Iran, water shortage and soil absorbable nutrients deficiency are limiting factors of plants growth. Nutrient deficiencies are compensated by chemical fertilizers. The main issue in fertilizer consumption is to use the optimal amount of fertilizer that ...
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Introduction: In arid and semi-arid regions such as Iran, water shortage and soil absorbable nutrients deficiency are limiting factors of plants growth. Nutrient deficiencies are compensated by chemical fertilizers. The main issue in fertilizer consumption is to use the optimal amount of fertilizer that increases water and fertilizer use efficiency. One of the newest and most effective approach for efficient use of water in agriculture is to magnetize the irrigation water. For producing magnetized water, it is crossed through a permanent magnetic field. By crossing water through a magnetic field, its physical and chemical properties improve. The aim of current research was, investigating the effect of urea fertigation by magnetized water on yield, water and fertilizer use efficiency in cucumber cv. Kish F1.
Materials and Methods: This study was performed as split plot experiment based on completely randomized block design with three replications from June to November 2018 on cucumber cultivate Kish F1 at the Research Farm of Agricultural Faculty, University of Zanjan, Iran. The treatments consisted nitrogen fertilizer levels at 5 levels from urea source (0%, 25%, 50%, 75% and 100% crop fertilizer requirement) and irrigation water (magnetized and no magnetized water). The treatment of 0% urea fertilizer and no magnetized water were considered as control. For crops irrigation, tape-drip irrigation system was used and for magnetizing of water, an electromagnetic field with 0.1 tesla was used. The crop water requirements were calculated by FAO-Penman-Monteith Approach on a daily basis using on-time weather parameters data of Zanjan Station. The irrigation frequency was 3 days. During the growth period, fertilization was done as fertigation approach on four times (15%, 30%, 30% and 25% of total crop urea fertilizer requirement). The first fertilization was applied 45 days after planting and the rests was carried out as 10-day periods after first fertilization.
Results and Discussion: The effect of urea fertilizer levels were significant at 0.1% level on yield, water use efficiency, number of fruits and leaf area, at 1% on chlorophyll index and at 5% on fertilizer use efficiency. Magnetized water was significant at 0.1% level on the all evaluated traits, except chlorophyll index. Treatment interaction effects were significant on water use efficiency, urea fertilizer use efficiency and number of fruits at 1% and no significant effect on the rest of traits. Compared with control, the highest and lowest increase in mean chlorophyll index were in 75% and 0.0% urea fertilizer level and magnetized water (21.1% and 0.4% respectively). At any urea fertilizer level, mean leaf area in magnetized water treatment was greater than no magnetized water treatment. Maximum and minimum difference between magnetized and not magnetized water treatments were in 25% and 0.0% urea fertilizer level (155.8 and 143.6 cm2, respectively). Based on treatments interaction, maximum mean of fruits number, achieved in 75% urea fertilizer level-magnetized water (32.8 number). It was 47.7% more than control. Maximum mean of cucumber yields with 50.3 t/ha, were in 75% urea fertilizer level-magnetized water that it increased 17.9, 2 and 3.8 t/ha compared with control, 100% urea fertilizer level-magnetized and no magnetized water, respectively. Results showed that application of magnetized water to irrigate plants, increased water use efficiency. Maximum water use efficiency achieved in 25% urea fertilizer level and magnetized water as much as 17.7 kg/m3. The trend of variations in mean water use efficiency showed, in no magnetized water, by reducing the application amount of urea fertilizer, averages of water use efficiency decreased but in magnetized water treatment, the trend of variations were incremental from 100% to 75% urea fertilizer level. On results, at each level of urea fertilizer treatment, using magnetized water for plant irrigating, increased mean of fertilizer use efficiency compared no magnetized water treatment. Maximum difference between means of urea fertilizer use efficiency at magnetized and no magnetized water was achieved in 25% urea fertilizer level as 74.3 Kg/Kg (367%). The results also showed, the trend of variations in mean urea fertilizer use efficiency at no magnetized water were decreasing from 100% to 25% urea fertilizer level but at magnetized water, the trend was increasing.
Conclusion: based on results of the current research, the optimum urea fertilizer level in Zanjan Region for cucumber is 75% urea fertilizer requirement, which by applying magnetized water to irrigate cucumber plants, mean of yield increases. In this case, in addition to save 25% of urea fertilizer amount, it is also prevented environmental problems.
behrouz hosseini; yaghoub dinpazhoh; J. Nikbakht
Abstract
Introduction: Drought is a creeping natural phenomenon, which can occur in any region. Such phenomenon not only affects the region subjected to drought, but its adverse effects can also be extended to other adjacent regions. This phenomenon mainly starts with water deficiency (say less than long- term ...
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Introduction: Drought is a creeping natural phenomenon, which can occur in any region. Such phenomenon not only affects the region subjected to drought, but its adverse effects can also be extended to other adjacent regions. This phenomenon mainly starts with water deficiency (say less than long- term mean of variable under study such as rainfall, streamflow, groundwater level or soil moisture) and progress in time. This period can be ended by increasing the rainfall and reaching the mean level. Even after the ending of a drought period, its adverse effects can be continued for several months. Although, it is not possible (at least at this time) to prevent the occurrence of drought in a given region, it is not impossible to alleviate the drought consequences by scientific water management. Such a management should be employed before drought initiation as well as during it and continue on even after the end of the drought period. The frequency of the main drought characteristics is a major concern of this study. The Northwest of Iran recently encountered severe and prolonged droughts, such that a major portion of the Urmia Lake surface disappeared during the last drought in recent years. In order to study drought characteristics, we used the Reconnaissance Drought Index (RDI). This index is based on annual rainfall and potential reference crop evapotranspiration (abbreviated by PET here). This study employed the Monte Carlo simulation technique for synthetic data generation for analysis.
Materials and Methods: The information from the 17 synoptic weather stations located in the North-west of Iran was used for drought analysis. Data was gathered from the Islamic Republic of Iran’s Meteorological Organization (IRIMO). In the first stage of research, the ratio of long term mean annual precipitation to evapotranspiration was calculated for each of the stations. For this purpose, the Penman-Montheis (FAO 56) method was selected for PET estimation. In the second stage, the 64 candidate statistical distributions were fitted for the mentioned RDI’s of each station. The best statistical distribution was selected among the 64 candidate distributions. The best fitted distribution was identified by the chi-square criterion. The parameters of the distribution were estimated by the Maximum Likelihood Estimation (MLE) scheme. Then 500 synthetic time series (each of them have the same number of observed data) were generated employing the parent population parameters. The three main drought characteristics (namely duration, severity and magnitude) were obtained for each of the mentioned artificial time series. The maximum values for each of the mentioned drought characteristic were selected for each year. Then, a new time series having the 500 elements were obtained by collecting the chosen values for each station. Once again the best distribution was selected for each series. Drought characteristics for different return periods (2, 10, 25, 50, 100 and 200 years) were estimated for each station.
Results and Discussion: Preliminary results indicated that a negative trend existed in annual rainfall time series for almost all of the stations. On the other hand, the pattern of monthly PET histograms were more or less similar for all of the selected stations. The peak of the PET was mainly observed in the hottest month of year, whereas the lowest value of the monthly PET belonged to the coldest month of year. The results showed that the amount of annual rainfall time series decreases sharply, after the year 1991. However, PET values significantly increase for all of the selected stations. After calculation of RDI values, the histogram of annual RDI’s was plotted against the year. This is repeated for all of the selected stations. Figure. 6 shows the mentioned diagram for Tabriz station as an example. In the mentioned Figure, negative values of RDI (shown by red bars) indicated the drought years. A critical prolonged drought with a sixteen years duration period (neglecting the 2001 in which RDI value was a small positive value) was experienced in Tabriz. The maximum drought severity in Tabriz was estimated to be about -7 in RDI units. Urmia station experienced the longest drought period, starting from 1995 and ending in 2005. It can be concluded that although few sparse wet years were observed in some of the selected stations in the studied period, they cannot compensate the water deficiency accumulated during several consecutive years. The results showed that the lowest value of the ratio of drought severity in a 100 year return period to the corresponding value for 2 year return period was about 2.13 (belonged to the Tabriz station), whereas the highest value was 3.17 (belonged to the Tekab station). On the other hand, the lowest value for the ratio of drought duration in 100 year return period to its corresponding value for 2 year return period was 1.95 (experienced in the Makoo station). The highest mentioned ratio was 9.18 (observed in the Sardasht station). The lowest and highest value of the ratio of drought magnitude in 100 year return period to its corresponding value for 2 year return period were 1.17 and 2.74, respectively. The mentioned drought magnitude ratios were observed in the Urmia and the Khalkhal stations, respectively. The isoplethes of the three main drought characteristics (severity, magnitude, duration) for a 10 year return period was illustrated for the study area (Northwest of Iran).
Conclusion: In the present study RDI values were used to analyze drought characteristics of Northwest of Iran. The Penman-Montheis method was used to estimate PET (needed for RDI) values of the stations. The main three drought characteristics were calculated for each of the 500 synthetic time series. The results showed that nearly all of the areas under study experienced severe and prolonged droughts. It can be concluded that a sharp decrease in annual precipitation as well as the increase in PET (due to greenhouse effects of consuming fossil fuels as the main source of energy in the region) from 1995 to 2005 was observed in the study area. Scientific management of available water in the study area is extremely vital to alleviate the adverse consequences of drought. Several economic and social problems were anticipated in these arid and semi-arid regions of Iran.
